Is my cat's eye injury serious?

Late last night, my cats woke me up while fighting.I noticed that one cat was holding one of her eyes only half open . When I looked more closely I could see a clear drainage (like tears) coming from the eye. I did not see anything in the eye and it looked OK. Today she has acted normal, and both eyes looked normal but I've caught her twice holding the eye half closed like she did last night. I've also observed a small amount of yellowish drainage aculate in the corner of her eye a couple of times today. I decided to inspect closer and when I pulled her lower eyelid down, the white part of the eye is really red. Other than that it looks normal. Of course, I'm scheduled to leave in the morning to go out of town until Friday. I'm debating on whether I should try to change my plans (will be expensive!) in order to take her to the vet, or can I just wait it out since she'd played, eaten and acted OK today?